Manufacture of felted proofed fibrous materials



Feb. 9, 1937. T. A. PASCOE ET AL MANUFACTURE OF FELTED QPROOFED FIBROUS MATERIAL Filed Sept. 1, 1932 FELTEU FIBERS. AND cawmss DERIVATIVE 10 //v co/vmvuous PHAS RES/Du: or HYDRATED CELL ULOSE CELL ULOSE' DER/WT/VE /N CONTINUOUS PHASE yf i m v Patented Feb. 9,' 133.7 7

MANUFACTURE OF FELTED PROOFED FIBROUS MATERIALS Truman A. Pascoe and Boy I. Hella, Cloquet,

Minn., assignors to Cellovis, Inc., Wilmington, I DeL, a corporation of Delaware Application September 1, 1932, Serial No. 631,410

21 Claims.

This invention relates'to the manufacture of sheets containing fibrous materials and cellulose derivatives soluble inorganic solvents but insoluble in water.

rial that is highly resistant to penetration of oils, greases, fats, waxes and the likeu A still further object is to prepare a material that retains its strength when in contact with water, and is at 10 the same time highly waterproof and resistant to the penetration of water vapor. Another object of this invention is to prepare a material that is highly translucent or transparent, and at the sametime strong and flexible. A particular object of our invention is to prepare a sheet containing hydrated cellulose fibers, a soluble cellulose derivative and a plasticizer thoroughly disseminated throughout the mass, and at the same time to provide a sheet that is highly translucent or even transparent,-

A still further object of the invention is to pro-" vide a sheet having a bodyor central portion containing fibers, a soluble cellulose derivative and a plasticizer thoroughly disseminated throughout the fibers, and one or more surfaces of plasticized soluble cellulose derivative,- which surface is an integral part of the composite sheet, being intimately united with the soluble cellulose derivative in the body or central portion of the sheet.

A'nother particular object is to provide a sheetlike structure the body of which is composed of a fibrous material having a soluble cellulose mate'- rial and a plasticizer therefor thoroughly dispersed therein, a surface coating of 'a soluble cellulose derivative, and modifying agents intive and plasticizers of the interior structure, said surface being of such a nature as. to be highly resistant to the transference of oils, fats, greases,

face of the sheet having a base of nitrocellulose and a plasticizer.

Other and ancillary, objects and advantages, and uses will appear in or be obvious from the following description and the appended claims.

For wrapping many articles it is highly desirable that the wrappingmaterial be both water and grease proof. Glassine' paper is highly grease and oil proof but has very poor water resistance. Papers, when waxed, as for example with. paraflin, have water resistance, but many Gil timately united with the soluble cellulose deriva- 5 An object, of this invention is to prepare a mate:-

greases soften the wax. Furthermore, the wax cracks on the folds, and 'such waxed paper is therefore unsatisfactory for many purposes. Regenerated cellulose, as found for example in viscose sheets, is grease-proof but has poor water resistance and low wet strength. Where resistance to water and water-vapor is to be obtained, products have been made of regenerated cellulose coated with a cellulose nitrate base lacquer, as for example, the'product described by Charch and Prindle in their U. S. Patent No. 1,737,187, .of November 26, 1929. Such a product, while resistant' to the transference of water vapor, is unsatisfactory for use in contact with wet materials and liquid water because the same cause the material to delaminate, weaken in strength, and lose its -water resistance and other valuable properties.

factory for use where low temperatures are encountered, such for example, as is described in U. S. patent to Birdseye, No. 1,773,079, August 12,

1930, on the freezing of foods in packaged-form.

According to the present invention the fibrous body may be readily coated with numerous agents without disadvantage, because the fibers of the base are encased in a continuous filling film which ,protects the fibers from injuryor change in fibers are preferred because of the varieties which are available, and because of the valuable characteristics which can be utilized, in the preferred formof this invention. In further detailed description, chemical wood pulp is specifically meant when the term pulp is employed, but in general many of the statements made regarding it are applicable to any fibrous pulp which may be used.

In carrying out our invention we employ as a base acomposition comprising a fibrous material. such as cellulose, a cellulose derivative that. is soluble in organic solvents but insoluble in water, and an agent to increase the flexibility of the cellulose derivative. We may also employ agents to render the material more resistant to permea- Furthermore, such products are very brittle at low temperatures making them unsatistion by water or water vapor, and we may also employ other modifying agents such as resins and coloring agents, as for example, dyes or pigments.

in many cases, and forspecial purposes, we prefer to apply a coating over the base sheet. Where such coating materials are used, we prefer to use a material having as a base a cellulose.

derivative insoluble in water, but soluble in organic solvents which are capable of also dissolving the cellulose derivative contained in the base sheet. For example, where the base sheet contains cellulose nitrate, we I prefer to employ a lacquer having a cellulose ester base as a coating material, dissolved in solvents which will also dissolve the cellulose nitrate in the base material. In such coatings we also employ a material to render the cellulose ester more flexible and elastic. In one valuable embodiment of our invention we also employ a resin or gum, either natural or synthetic; such as ester gum or a chlorinated diphenyl resin, and an agent to render the material more vresistant tothe penetration of water vapor, as for example, stearic acid.

The exact proportions of the various ingredients will vary according to the qualities desired in the finished product, and the use to which the product is to be put. The following more detailed descriptions illustrate several ways of obtaining a material having desirable properties described above. It will he apparent, however, that wide variations are possible in .the choice of materials, in the proportions used and in the manner in which they are combined.

A' paper-forming stock may be made of water, cellulosic pulp and a cellulose derivative soluble in organic solvents with or without modifying agents. Such a mixture maybe beaten, as in preparation for paper formation. on a Fourdrinier or cylinder paper machine. beaten to any predetermined freeness, indicat ing an extent of hydration; it may be partially hydrated or it may be highly hydrated. There is no difllculty in felting stock of cellulose fibers and nitrated wood cellulose fibers, or other fibrous cellulose derivative, whatever the proportion of the two fibers up to practically 100% of nitrocellulose fibers. Such proportion is however inordinately beyond the requirements for the preferred usages of the invention. At 70% nitrocellulose fibers and 30% cellulose fibers, the, resulting felted sheet has an appearance of an ordinary sheet of paper. At 10% nitrocellulose fibers and cellulose fibers the resulting felted sheet has all of the essential characteristics of a sheet made out of of that same cellulose fibers.

Wherethe base material is to be used directly,

we prefer a hydrated cellulose in combination.

with, for example, cellulose nitrate, or cellulose acetate, and a plasticizer for the cellulose ester with or without other modifying agents. The hydrated cellulose, such as hydrated chemical wood pulp is especially useful where a high resistance to organic solvents, to oils, fats, greases, etc., is to be obtained; A highly hydrated cellulose is also desirable where a high degree of transparency or translucency is desired, and we have found that highly transparent and translucent sheets may be made from mixtures of hydrated cellulose and nitrocellulose. The degree of hydration of cellulose affects its freeness, so that a highlyhydrated cellulose has a low freeness, and consequently must be run slowly on a paper ma chine, resulting in a low per diem production. We have found that by the addition of a cellulose derivative, such as cellulose nitrate fibersito this hydrated stock, the freeness is greatly increased, so that we may either increase the speed of the paper machine for a cellulose of a given hydra- The stock may be esters or ethers in such sheets of hydrated celi lulose do not render the sheet permeable to such solvents. Not until a substantially large proportion of such esters or ethers are present does such a sheet become permeable to such solvents. We have discovered that inorder to secure penetrability by such solvents ity is necessary to increase the proportionof soluble fibers, or to decrease the degree of hydration, or to do both.

It is not practical, therefore, to makea paper like sheet of say 95 parts of awood cellulose hydrated to a freeness of (Green) and 5 parts of nitrocellulose, -and then to wet ,the sheet with nitrocellulose solvents, as for example, ethyl or butyl acetate, in order to dissolve the particles of nitrocellulose and cause them to coalesce. The hydrated cellulose prevents the nitrocellulose solvents from penet ating the sheet so that even after five or ten minutes in contact with dry solvents, the nitrocellulose fibers in the interior of the sheet retain their fibrous form.

' We are aware that it is old to mix fibrous ma- .terial such as wood pulp or rag stock, asbestos, leather fibers, etc., with a cellulose ester or ether,

and then form the mixture into a sheet. It is also old to wet a sheet so formed with an organic solvent capable of dissolving the cellulose ester or ether and causing it to coalesce and form a. more or less continuous film. Such processes as have been described, however, are not applicable to a sheet made of cellulose that has been hydrated to the point where it is resistant to the "penetra: tion of oils, fats, greases, etc., for the reasons already pointed out.

In order to increase the penetrability of such a sheet to the usual non-aqueous solvents, it is necessary either to increase the proportion of nitrocellulose, or to decrease the degree of hydration. For example, when a stock containing 20% nitrocellulose fibers and 80% hydrated (freeness 120 Green) cellulose fibers isfelted, the resulting sheet is easily penetrated by a non-hydrous r Percent Ethyl acetate 40 Butyl acetate; 10 Toluol 35 Castor oil e 10 Tricresyl phosphate 5 For a given proportion of cellulose derivative there is a limiting degree of hydration when a specific solvent is to be applied for solution of the cellulose derivative. The limiting factors may be readily determined by experimentation with the specific materials, and other conditionssuch as there is less need for considering the degree oi 90% of a wood cellulose hydrated to a freeness of 120 (Green), and 10% of nitrocellulose, was extremely difllcult to wet with a solvent composed of Percent Ethyl acetate Butyl acetate l0 Toluol 35 Castor oil 10 'Iricresyl phosphate whereas a sheet made from 80% of a similarhydrated cellulose, and 20% cellulose nitrate was quite easy to 'wet with the above solvent.

Where we use a hydrated cellulose, a cellulose ester and a plasticizer for the cellulose ester, we have been able to obtainas by hot calenderi'ng, a sheet having a high degree of transparency, which is also much more flexible and stronger than, for example, glassine paper. A sheet made by this process retains its strength under water to a surprising degree, and is substantially water proof. It also is more highly resistant to penetration by water vapor than ordinary glassine paper.

Another manner of obtaining our desired product is to make use of a plasticizer which may be added atthe beater, which is a solvent for the cellulose, ester, and then pass the sheet be-.

tween heated rollers under high pressure, preferably as in a paper calender or super calender, whereupon the particles of cellulose ester and plasticizer coalesce and embed the hydrated cellulose, filling up interstices of the paper. I In this process it is not necessary to use a volatile organic solvent to dissolve the cellulose ester, al-

though it may sometimes be desirable to do so..

To secure a high degree of moisture and grease proofness, flexibility, and transparency, we prefer to employ, for each parts by weight (dry weight of cellulose) of hydrated cellulose, at least 6 parts of nitrocellulose and a suitable amount of plasticizer depending upon the results desired.

These may be mixed in a paper beater until substantially all 'of the plasticizer has been taken up by the stock, and then run on the paper machine. Surprisingly enough, we have found that the addition ofthe nitrocellulose and the plas-v ticizer to the hydrated stock does not slow up the rate at which it may be run on the paper making machine. After drying in the usual paper mill drier, such a. paper is highly translucent, flexible and waterproof.' Our preferred process, however, contemplates treatin the sheet formed as described above by an ironing process, as in a paper calendering or super calendering machine. The calendering treatment causes the nitrocellulose to dissolve in the solvent plasticizer and to coalesce, and at the same timefurther increases the transparency of the hydrated cellulose, thus producing a highly transparent and glazed sheet, thatis highly resistant to water,-grease, fats and oils, and which is highly resistant to water vapor and to oxygen and other gases.

In order that the invention may be made clear, the following examples are given by way of illustration. It is, of course, to be understood thatthe examples are not to be taken as limiting the scope of the invention, since they are given merely by way of illustrating how some of the details of the process may be carried out.

Example I pulp. 25 lb. of dibutyl phthalate and '70 lb. of

castor oil are then added, ,and mixing in the beater continued until substantially all of the dibutyl phthalate and castor oil has been taken up on the fibers.

The beater is then discharged into the chest and water added. The stock is then run through Jordan machines, and made into paper furnish by adding additional water if necessary to produce the proper weight of paper. Ordinary paper makers practice is followed, bearing in mind increased freeness due to the nitrocellulose.

The paper is made on any suitable paper making machine in the usual manner. The paper so made is somewhat translucent, and is water repellent. In order to secure the full benefit of the nitrocellulose and plasticizer we prefer to subject the paper to an ironing process. For this purpose, heated calender rolls are-satisfactory. The paper as made above is therefore run through calender rolls, or preferably through a super calender, the rolls of which are heated to a temperature of not less than F.

Example H Weight)' is placed in a heater and beaten to a fr-eeness of 100 (Green); 3001b. of cellulose ni- 700 lb. of bleached chemical wood pulp (dry trate is then added and the hydrated cellulose and nitrocellulose are thoroughly mixed. The above stock is made into sheets in the same manner as described in Example I, or by any ordinary paper making procedure. We have found that where a hydrated wood pulp cellulose is used, nitrocellulose prepared from wood pulp cellulose, such as that made according to the process described in the U. S. patents of Wm. zcourtney Wilson, No; 1,883,215 of October 18,

makes it less detectable as a foreign fiber in paper stock, and its small size limits the spacing between the cellulose fibers.

Where the sheet of mixed insoluble fibers and soluble inclusionsis to'be coated with a cellulose ester or ether basesolution, a wider choice of specific base materials-is possible. Our inven'tion, therefore, contemplates broadly the use of any fibrous materials having dispersed therein a cellulose ester or ether soluble in the solvents employed for the coating solution, when coated with a coating material such as is hereinafter described. ;We may use, for example, mixtures of cellulose ester or ether with suchflbrous -mate- 1932, and No. 1,925,162 of September 5, 1933, is I rials as wood pulp cellulose, wool, leather fibers, asbestos and like fibrous materials.

For the sake of clarity the following description is confined to fibers of wood pulp cellulose scription, other soluble esters or ethers of cellulose may be used either alone or as mixtures without departing from this invention.

In carrying out our invention as applied to a composite sheet, coated on one or both, sides, we first make up a sheet consisting of wood pulp cellulose having cellulose nitrate dispersed therein, A satisfactory method of securing such a sheet isto place the wood pulp and the cellulose nitrate in a paper beater and operate the beater either as a beater or a mixer until a uniform mixture is secured. We may also at this time add other materials in the beater, such as siz-, ing agents, coloring matter such as dyes and/or pigments; agentsfor plasticizing the nitrocellulose, fillers, and the like. After thorough mixing, the stock is formed into a sheet, as for example, on a-paper making machine, or, where sheets havin a considerable, thickness are desired, on a multiple cylinder machine. In formingthe sheets on such machines, most of the water is removed, and in most instances the sheet may be handled in a manner similar to thehandling of ordinary paper pulp products.

Wide variations in the proportions of wood pulp and cellulose nitrate are possible, and the proportions maybe varied according to the product desired. In some cases, where it is merely desired to secure Rood adherence between the base sheet and the coating, as little as 5 or 10 per cent of nitrocellulose may be used. -On the other hand, where a highly water proof material is desired, a larger amount, sayfrom 15% to 40% of nitrocellulose is to be preferred. In still other cases, where flexibility, transparency, or other special properties are desired, the nitrocellulose may predominate, and as much as 85% or 90% of nitrocellulose may be used advantageously.

The type of fibrous material selected, will be determined by the requirements of the product. Where a high tensile strength is desired, a long fiber such as kraft pulp, wood fiber cooked by a neutral sodium sulfiteprocess, or fiax fiber may be used. Where transparency is desired, a hydrated cellulose such as described in Examples I and II is useful in our process and these examples may be considered as one suitable form of base sheet. Where heat resistance is desired, asbestos] fibers in combination with acellulose ether such as ethyl cellulose gives a desirable base. After a proper base; sheet such as described above has been prepared, we apply a coating on one or both sides. of the sheet. We are able to secure perfect adherence between the base and the coating by employing solvents for the coat ing materialthat are also [solvents for the cellulose ester or ether in the base-sheet. For example, imhebase sheet contains cellulose nitrate, we may use as a coating material cellulose n1 trate-and a plasticizer dissolved in a suitable sol- ,vent such-as described in some following exampies. If the base sheetcontains cellulose acetate,

we may use cellulose acetate and a 'plasticizer dissolved in a solvent such as is described in some following examples, which solvent is capable of dissolving the cellulose acetate contained in the base sheet. We also contemplate using in the coatingcellulose esters or ethers which are different from the cellulose ester or ether contained in the base sheet, provided the solvent used for the coating material is capable of dissolving the cellulose ester orether used in the base sheet. .Thus we may use cellulose nitrate in the base sheet, and a coating material containing cellulose acetate and a plasticizer dissolved in a solvent also capable of dissolving the cellulose nitrate used in the base sheet. We thus secure a structure wherein the surface area is continuousand microscopically homogeneous, and is integral and continuous with the continuous phase of the base sheet. i

In order to illustrate the product of the present invention .a representative drawing is made of exemplary embodiments of the invention.

Fig. 1 illustrates a felted fibrous sheet in which the solublecellulose derivative, originally present during feltingas discrete units, is coalesced into an integral. body as a continuous phase in the sheet.

Fig. 2 isa sheet similar to that of Fig. 1, in

which a coating film on the two surfaces is integrally united to the continuous phase, having highly hydrated. Thus they are united to each other by the dried residue of hydrated cellulose. Should these fibers be other than hydrated cellulose, to which the latter substance hasbeen added in the paper forming stock, substantially the same condition will obtain. The numeral ll designates the continuous phase which houses the fibers comprising as a base a soluble cellulose derivative, with or without modifying agents, added either in the paper furnish, or thereafter to the felted sheet.

The paper sheet of Fig. 1 contains material soluble in organic solvents. Usingsuch a sheet in character which is penetrable by a suitable solvent, a coating may be applied which can be anchored to and integrally united with the continuous phase II of the sheet.

Fig. 2 represents such a product formed from a structure like that of Fig. 1. Although both surfaces are coated, the coating of one surface only is contemplated. In Fig. 2 there is a body portion II, a surface portion l3, and a second surface portion l4. The body portion contains felted fibers I5, and a continuous phase of coalesced cellulose derivative It, as described for Fig. l. The surface layers may be the same or different in composition, but each comprises essentially a base material capable of application 'for integral union with the material It. Cel

lulose esters and ethers arefsuitable. It is preferred that the bases of material l8 and of a which in the paper forming stock had been are protected by the integral continuous material which runs from surface to surface.

Our preferred coating is most conveniently applied from a solution, but we may also apply it as a sheet, by wetting the base sheet and/or the coating sheet with a solvent capable of dissolving both the coating sheet and the cellulose ester or ether in the base sheet, and pressing the two sheetstogether. 4

Our preferred coating material consists essen-- tially of a solution ofv cellulose ester or ether in a solvent capable of dissolving the cellulose ester or ether in the base materlal'. v In most cases it is desirable to have present also a plasticizer forthe cellulose ester or ether employed, to increase the flexibility and elasticity of the coating. Such plasticizers, are well known in the art. For example, suitable plasticizers for cellulose nitrate are dibutyl phthalate, tricresyl phosphate, castor oil, and certain balsam-like resinous materials.

ployed, that is, upon evaporation of the solvent,

the film should have. the appearance of bein homogeneous.

We may also use coloring materials such as pigments or dyes, either in solution or in suspension in the coating material, to produce color effects. For some purposes metal powders such as the well known bronze or aluminum powders may be used. Furthermore, we may add to the coating solution a soluble material which, upon evaporation of the solvents, crystallizes out in the coating layer to form crystalline designs, such as are ,obtained by the crystallizing lacquers. Phthalic acid is useful in a nitrocellulose base coating for crystallizing effects.

Where water proofness, and especially water vapor proofness is important, we may use a coating material designed to increase the moisture proofness of the base sheet. For example, we may add to the coating compositions such materials as fatty acids having more than 12 carbon atoms as for example, palmitic and stearic acids. We may also employ for the same purposes, various waxes or waxy materials such as spermacetti wax, or parafiin wax, and other materials known to aid in preventing the penetration ofwater vapor.

The following examples of suitable coating compositions'are given merely by way of illustration, and are not to be considered as limiting the broader aspectsof the invention.

' Example III L Parts by weight 'Nitrocellulose Castor oil v 60 .Dibutyl phthalate 40 Toluol- 360 Alcohol 40 Butyl acetate .250

Ethyl acetate Suitable plasticizers for cellulose ace--' tates are tricresyl or triphenyl phosphate, t0lu- This coating solution is suitable for use where a high degree of flexibility is desired. It is substantially unaffected by water, but is not water vapor proof; The solvents in a composition asgiven above will dissolve cellulose nitrate in the base sheet, and cause it to blend with the nitrocellulose, resulting in an integral substance extending as a. continuous phase throughout the sheet.

The resin may be any resin compatible with nitrocellulose, such as ester gum, phthalic acidglycerol resins, damar, shellac, etc. Thesolvent may be any solvent or mixture of solvents capable of holding the non-volatileingredients in solution until substantially all the solvent has evaporated, such for example, as the solvent mixture given in Example IV. The above lacquer ishighly resistant to the penetration of water and water vapor.

Erample VI Cellulose acetate Toluene ethyl sulfonamidnn 175 Parts by weight Acetone l. v 212 Methyl ether of ethylene glycol 50D Alcohol (ethyl). 200

The solvent given. in this example is capable of dissolving not only acetone soluble types of cellulose acetate, but will also dissolve cellulose nitrate and most of the cellulose ethers. -It is useful, thereforejin combining a cellulose ace tate surface layer to a base sheet having a cellulose acetate, cellulose nitrate or cellulose ether therein. The solvent may be used with cellulose nitrate or the cellulose ethers for applying cellulose nitrate or cellulose ethers as a coating to base sheets having a cellulose acetate therein.

Example VII Parts by weight Ethyl cellulose L .100 Tricresyl phosphate 25 Spermacetti wax 25 Resin 15 Solvent 1 00 The solvent should be chosen that is capable not only of holding the ethyl cellulose and other non-volatile ingredients in solution, but which formation of the sheet, it is to be observed that in the finished sheet the soluble fibers are coalable resistant properties, like glassine paper.

The soluble material therein serves to increase the normally low freeness of the furnish. In the finished product such material may be coalesced to a degree at the surface when a solvent, as in an applied lacquer coating, is used to wet the surface. Thus it serves to anchor the felted sheet, either to a coating or to any surface which is wet with a suitable solvent.

Inasmuch as productsembodying the present invention are contemplated for extensive use in substitution for papers or sheets now known, it is in the interest of economy and low cost to reduce to a minimum the amount of soluble cellulose derivative. Every endeavor is made, therefore, for any special use, to secure the desired properties with as low a content of the more expensive ingredients. It is therefore contemplated that for special uses there may be departures from the specific illustrations herein given, with respect to the ingredients required, the proportion, andthe treatment in process. Anyone skilled in the art may do this after fully comprehending the exemplary disclosures here made.

Whatever the fibers are which form thebody of the material we have found that the presence of hydrated cellulose in the paper forming stock has a profound eifect upon the character of sheet which results. It is well known that this may be produced by mechanical action on cellulosic fibers in water, forming a gelatinous film of hydrated cellulose on the fibers, or even converting the fibers almost entirely intoa gelatinous mass. In our preferred usage of chemical wood pulp, we may hydrate the fibers, retaining fibrous characteristics, but it is to be understood that we may use other fibers and add to the stock a hydrated cellulose in gelatinous or in fibrous form.

The product like Fig. 1 may be used for wrappings as on food, packages, wall paper, linings,

paper dishes, as a parchment substitute, lamp shades, as a receiver for a finishing coat.

The product like Fig: 2 may be used for substantially all the uses above given and may have many special uses, such as where a highly finmoisture-proofness is required. It is understood that either one or both sides may be finished with coating material, and the utility for special 'purposes thus regulated as desired.

Many other modifications and different embodiments of. the invention will be found useful in numerous arts and in numerous combinations. In the appended claims we aim to define the invention as including all the forms herein described and suggested and all such departures and modifications of the'process and the product a which fall within the scope of the invention as defined by the claims.

Matter disclosed herein is described and claimed in a subsequent application Serial No. 3,032, filed January 23,1935, as a continuation in part of this application in response to a requirement for division.

We claim:

1. The method of making a paper-like sheet which comprises hydrating cellulose, felting into sheet form a paper-forming stock of said hydrated cellulose and fibrous material and a finely divided cellulose derivative, and drying said sheet.

2. The method of making a paper-like sheet which comprises hydrating cellulose to form hydrated cellulose, felting into sheet form a paperforming stock containing said hydrated cellulose, fibrous mat ial, a finely. divided cellulose derivative, and a p asticizer therefor, and thereafter coalescing the cellulose derivative into a continuous phase in the resulting sheet.

3. The method of making a paper-like sheet which comprises hydrating cellulose, felting into sheet form a paper-forming stock of said M- drated cellulose and fibrous material and a finely divided cellulose derivative, and thereafter coalescing the cellulose derivatlve'into a continuous phase in the resulting sheet. v

4. The method of making a paper-like sheet which comprises hydrating cellulosic fibers to form a slow-stock, felting into a sheet sald stock I and a finely divided cellulose derivative, and

thereafter coalescing the cellulose derivative intoa continuous phase in the resulting sheet.

5. The method of making a paper-like sheet which comprises hydrating cellulosic fibers to form a slow-stock, felting into a sheet said stock and a fibrous cellulose derivative, and thereafter coalescing the cellulose derivative into a continuous phase in the resulting sheet.

6. The method of. making a paper-like sheet which comprises hydrating cellulosic fibers to I form a' slow-stock, felting into a sheet said stock containing a fibrous cellulose derivative and a plasticizer-therefor, and thereafter coalescing the derivative and plasticizer into a continuous phase in the resulting sheet.

8. The method of making a paper-like sheet which comprises hydrating cellulosic fibers to form a slow-stock, felting into a sheet said stock 7 containing nitrocellulose in fibrous form, and thereafter coalescing the nitrocellulose into a continuous phase in the resulting sheet.

9. The method of making a paper-like sheet which comprises hydrating chemical wood pulp to form a slow-stock, felting into-a sheet said stock containing nitrated wood pulp fibers, and

thereafter coalescing the nitrocellulose into a continuous phase injthe resulting sheet.

10. The method of making a paper-like sheet which comprises hydrating cellulosic fibers to form a slow-stock, felting into a dried sheet said stock containing a quantity of finely divided cellulose derivative capable of forming a sheet permeable to an organic solvent for said derivative, and applying such a solvent to the sheet for coalescing the derivative into a continuous phase in said sheet. r 5

11. The method of makings paper-like sheet which comprises hydrating cellulosic fibers to form a slow-stock, felting into a dried sheet said stock containinga quantity of finely divided cel- 78 lulose derivative capable of forming a sheet permeable to a volatile organic solvent for said derivative, applying a-mixture of such a solvent containing a plasticizer for said derivative. whereby to distend the derivative in the sheet, and

evaporating the solvent.

12. A dried felted sheet comprising felted fibers. the dried residue of hydrated cellulose, and a finely dividedcellulose derivative.

13. A dried felted sheet comprising felted fibers, the dried residue of hydrated cellulose, and fibrous cellulose derivative.

14. A dried felted sheet comprising thedried residue of felted highly hydrated cellulosic fibers, and finely" divided cellulose derivative.

15. A dried felted sheet comprising the dried residue of felted highly hydrated cellulosic fibers and finely divided nitrocellulose.

16. A dried felted sheet comprising the dried residue of felted highly hydrated cellulosic fibers and nitrated cellulose fibers.

17. A dried felted sheet comprising the -dried residue of hydrated cellulose, felted fibers, and

a cellulose derivative extending throughout the sheet as a continuous phase in said sheet.

said sheet. a

19. The method of making a paper-like sheet which comprises hydrating cellulose until it is capable of forming with fibers a grease-proof sheet, felting into sheet form a paper-forming stock containing said hydrated cellulose and finely divided cellulose derivative, and drying said sheet.

18. A dried felted sheet comprising the dried. residue of hydrated cellulose, felted fibers, a d a plasticized cellulose derivative extendigg 1 throughout the sheet as a continuous phase in 21. A fibrous sheet comprising felted fibers, the

.residue of hydrated cellulose, and a continuous phase of modified cellulose derivative containing said fibers, said modified derivative containing a resinous modifying agent.

' p I TRUMAN A. PASCOE.

' ROY P. BELLA. 

